1. Field of the Invention
This invention relates to an electromagnet wherein a cylindrical fixed core and a cylindrical movable core are accommodated inside a tubular coil and the movable core is shifted towards and attracted to the fixed core under a magnetic force exerted between both cores due to a magnetic flux produced through each of the cores by energizing the coil and more particularly to a process for manufacturing a magnetic core constitution used as a fixed core, a movable core or the like.
2. Prior Art
An electromagnet of this type is disclosed, for example, in U.S. Pat. No. 3,633,139. If the core is formed of a solid material, high eddy current is generated when current flows through the coil to impart the magnetic flux to the core. This gives rise to a problem in that a great heat generation occurs. A further problem occurs wherein electric power applied to the coil is wastefully consumed for said heat generation. In view of the foregoing, as cores free from these problems as noted above, a core having a number of core elements, which are formed from thin steel sheet, laminated has been extensively used. However, it takes time and labor to make these cores. That is, as shown in FIG. 20, plural sheets of core elements 111, 112 and 113, which are different in side shape from one another, are prepared. Next, these elements are superposed one upon another in a way that order and the number of sheets are correct. Then, these core elements are connected together by means of self-locking pins 114 while holding them inseparably. Subsequently, the thus connected elements are cut by a machine tool such as a lathe into the required shape as shown by the dash-dotted contour lines at 115. Many steps as mentioned above are necessary.
In addition, the core fabricated as described above has its core elements which are variously different in shape and dimension. Thus, when shocks are applied during the use of the electromagnet, forces received by each of these elements are different from one another. Therefore, while the aforesaid shocks are being repeatedly applied, the core elements are displaced one another with the result that the core becomes deformed.